The present invention relates to a roasting apparatus allowing automation of a roasting process including steps of charging a raw material to be roasted, roasting the raw material, and carrying out a roasted product.
A known roasting apparatus includes a roasting kiln formed into a circular shape or an elliptic shape in cross section.
&lt;Drying/Roasting Step&gt;
A circular roasting kiln in which rotary blades are mounted in the roasting kiln is known from Japanese Patent Publication Nos. Hei 4-17623 and Hei 5-5463. In this roasting kiln, the rotary blades are rotated upon roasting, to roast a material to be roasted.
Another circular roasting kiln in which a number of agitating blades spaced at specific intervals are projectingly formed on the inner peripheral wall surface of the roasting kiln is known from Japanese Utility Model Publication No. Hei 7-26951. In this roasting kiln, a material to be roasted, which is accumulated on the bottom of the roasting kiln, is scooped up by the agitating blades, and when the agitating blades reach the top of the roasting kiln, the material to be roasted is dropped.
An elliptic roasting kiln is known from Japanese Patent Publication No. Hei 3-56726, wherein a material to be roasted, which is accumulated on the bottom of the elliptic drum, is lifted upward and then dropped to sufficiently agitate the material to be roasted, thereby effecting uniform drying and roasting.
&lt;Dipping Step&gt;
A quantitative tank is used at the dipping step before roasting. At this dipping step, an operator has performed works of previously charging grain and water in the quantitative tank, dipping the grain in water in the quantitative tank, opening the bottom of the quantitative tank after the grain is sufficiently dipped in water, and charging the grain in a roasting kiln of the roasting apparatus.
However, the following problems are encountered in automating a roasting process including steps of dipping a raw material to be roasted in water and roasting the raw material to be roasted using the related art roasting apparatus.
&lt;Dipping Step&gt;
(1) The dipping step involves works of loosening a string having bound the end portion of a net bag, provided in the quantitative tank, for containing a raw material to be roasted, and charging the raw material to be roasted in a roasting kiln. The works are manually performed by an operator, thereby taking a lot of labor and processing time, and further, the works must be performed by an operator in such a severe working environment that the temperature in the work section is high by the thermal effect of the roasting kiln. For this reason, it may be desired to automate the dipping step.
(2) If the quantitative tank is disposed apart from the roasting kiln, since a raw material to be roasted, which has been dipped in water and taken out of the quantitative tank, must be immediately charged in an opening of the roasting kiln without being scattered to the outside, attention must be paid to arrangement and structures for mounting the quantitative tank and roasting kiln to each other and to the procedure of charging the raw material to be roasted in the roasting kiln. PA1 (3) For a roasted product having a water content of 6%, the gelatinization degree of starch is about 30 to 40% which is low insufficient for the roasted product to be used as a drinkable health food or a drink. To improve the digestion characteristic of the roasted product, it is required to enhance the gelatinization degree of the roasted product. In particular, a roasted product of unpolished rice is indigestible, and therefore, it may be desired to enhance the gelatinization degree of the roasted product of unpolished rice. PA1 (4) In the case of roasting grain for a long time such as several hours until it is charred, it is difficult to uniformly heat the grain with strong fire. This is because strong fire burns only the surface of the grain and does not sufficiently heat up the interior of the grain. As a result, in the above case, the grain is required to be heated with weak fire or by controlling a fire power. To produce weak fire or control a fire power, however, the external gas heating is degraded in terms of safety, reliability and controllability. PA1 (5) To take a roasted product out of a roasting kiln, there is adopted a method of rotating rotary blades or the rotary kiln in the direction opposed to that upon roasting by a motor and taking the product from a discharge port formed at one end of the roasting kiln. In this method, the use of a roasting kiln having a circular cross section presents a problem. That is to say, a raw material is only slipped on part of the inner peripheral surface of the circular roasting kiln, and thereby it is not agitated during take-out of the product. As a result, part of the raw material in contact with and in the vicinity of the inner wall of the roasting kiln is strong heated, while part of the raw material separated from the inner wall of the roasting kiln is not heated. In this way, it is difficult to uniformly roast the raw material. PA1 (6) In usual roasting for obtaining a product having a water content of about 3 to 14%, the roasting time is as relatively short as 20 to 45 minutes. In this case, according to the related art method, since the raw material is externally heated via a roasting kiln, the thermal conductance is poor. This makes longer the roasting time, to degrade the quality of a roasted product due to thermal deterioration of the product. PA1 (7) At the roasting step, according to the related art method, there occurs a difference in uniformity between roasted products depending on a difference in the rotational speed of a roasting kiln, a difference in agitating state of a material to be roasted due to the charged amount in the kiln, and a difference in water content of the grain between the initial, medium and final stages at the roasting step. Further, the roasting time requires 30 minutes for each roasting, resulting in the reduced productivity. For this reason, it may be desired to improve the productivity without degradation of the quality. PA1 (8) In the related art method, the termination of roasting is determined by setting the roasting time using a timer; however, the finishing water content of a roasted product is dependent on the atmospheric temperature and moisture, the dipping state of a raw material, or the initial state or the final state of the roasting operation continuously performed throughout one day, to thereby obstruct the uniformity of roasted products.
&lt;Drying/Roasting Step&gt;
The use of a roasting kiln having an elliptic cross section presents another problem. That is to say, the roasting kiln having an elliptic cross section can uniformly roast a raw material; however, it cannot be provided with rotary blades. In particular, since the temperature of the interior of the kiln is high, it is impossible to mount drive portions of a motor or hydraulic equipment. As a result, a roasted product is manually taken out by an operator, which takes a lot of time. Also since the rotation of the roasting kiln is stopped during take-out of the roasted product, the product accumulated in the roasting kiln is excessively heated, giving rise to inconveniences, such as occurrence of unevenness of roasting, obstruction to labor-saving, or an increase in processing time.